1. Field of the Invention
This invention is in the field of pharmacology, and relates to multi-component formulations, which contain metformin, a sulfonylurea or a combination of both, in concert with one or more other active ingredients, for use in the pharmacological treatment of insulin resistance and type 2 diabetes mellitus.
2. Description of the Prior Art
Insulin resistance and non-insulin-dependent diabetes are prevalent in up to 35% of the population depending upon the age and nature of the subset. In the United States alone, 16 million people have type 2 diabetes and 13 million have impaired glucose tolerance. In fact type 2 diabetes has reached epidemic proportions worldwide. By 2025, an estimated 300 million people will have diabetes, most of who will inhabit China, India, and the United States. Because of an aging and increasingly sedentary, obese population with changing, unhealthy diets, insulin resistance is also increasing alarmingly (it is already two to three times more prevalent than type 2 diabetes). This apparent increase in the prevalence of insulin resistance and type 2 diabetes occurs in all ethnic populations, but especially in those that have migrated from their native lands to more urbanized and westernized regions of the world.
Insulin resistance and type 2 diabetes exist not merely as part of the aging process, but also as a process that advances aging. Diabetes affects metabolism in totality: carbohydrate, lipid and protein. Its causes and its management are very, very complex and strikingly nonlinear.
Patients with diabetes of all types have considerable morbidity and mortality from microvascular (retinopathy, neuropathy, nephropathy) and macrovascular (heart attacks, stroke, peripheral vascular disease) pathology, all of which carry an enormous cost. For example: a) Proliferative retinopathy (the leading cause of blindness in the United States) and/or macular edema occur in about 50% of patients with type 2 diabetes, as do peripheral and/or autonomic neuropathy. b) The incidence of diabetic renal disease is 10% to 50% depending on ethnicity. c) Diabetics have heart attacks, strokes and peripheral vascular disease at about triple the rate of non-diabetics. The cost of treating diabetes and its complications exceeds $100 billion annually. In addition to these dreadful data, insulin resistance (a prelude to type 2 diabetes in about 50% of those effected) with its associated hypertension, coagulopathy, dyslipidemia and obesity substantially adds to these morbidity, mortality and cost statistics.
There are two clinical forms of diabetes, each with a different pathogenesis: type 1, insulin dependent diabetes mellitus and type 2, non-insulin dependent diabetes mellitus. The latter represents 90% of all diabetics. In type 2 diabetes, cellular resistance to the functional effectiveness of insulin results in above normal levels of insulin secretion. When this compensatory increase of insulin production cannot be maintained, and/or when cellular insulin resistance increases further, blood sugar rises, lipid and protein metabolism are disturbed, and the insidious processes of vascular complications of long-term diabetes begin.
The fasting hyperglycemia of type 2 diabetes exists in the presence of hyperinsulinemia; this reflects the presence of insulin resistance in the liver with resultant glycogenolysis and gluconeogenesis. In addition to the impaired insulin suppression of hepatic glucose production, a decrease of insulin-mediated glucose uptake by muscle cells contributes (about 50%) to the resultant hyperglycemia.
After ingestion of glucose, the maintenance of normal blood sugar therefore depends upon: 1) stimulation of insulin secretion; 2) insulin-mediated suppression of hepatic glycogenolytic and gluconeogenic glucose production, and 3) insulin-mediated glucose uptake by muscle. Although hyperglycemia has an independent, direct effect in suppressing hepatic gluconeogenesis and stimulating muscle glucose uptake, these effects are modest compared to those of insulin and are inadequate to compensate for the countering effects of insulin resistance.
The congeries of micro and macro pathologies from hyperinsulinemia and/or hyperglycemia have as causative mechanisms: free radical damage, nonenzymatic protein glycation, lipoprotein disturbances, disturbances of physiological NO effects, reduced synthesis of heparan sulfate and disorders of sorbitol and myoinositol metabolism.
Free radical generation and induced nitric oxide synthase (iNOS) production secondary to the hyperglycemia of type 2 diabetes can lead to pancreatic xcex2-cell destruction, and the production of diagnostic enzymatic indicators characteristic of type 1 diabetes. This fact has introduced the term xe2x80x9ctype 1.5 diabetesxe2x80x9d. In this scenario, xcex2-cells are not only xe2x80x9cexhaustedxe2x80x9d by the progression of pathology from insulin resistance to type 2 diabetes, but may also undergo destruction induced by chronic hyperglycemia.
Hypertension, dyslipidemia, coagulopathy, obesity and development of type 2 diabetesxe2x80x94all of which may follow chronic insulin resistancexe2x80x94are largely preventable, as are the eventual diabetic micro- and macrovascular complications. In those patients with insulin resistance who do progress to type 2 diabetes, successful treatment requires maintenance of blood glucose at a normal preprandial level (or at a postprandial level below 180 dl) and a hemoglobin A1c level below 7.0%. This degree of glucose control is often not consistently attainable over long periods of time.
Likewise, good glycemic control avoids the impaired synthesis of the basement membrane proteoglycan, heparan sulfate, which accompanies hyperglycemia. Heparan sulfate is an essential component of the basement membrane of many cells. Most importantly, it supports many of the normal functions of endothelial cells by maintaining the integrity of the basement membrane and its anionic charge, both of which are critical in maintaining physiologic membrane impermeability: It is the predominant glycosaminoglycan produced by the glomerular epithelial cells. Microproteinuria, due to its inadequacy in the glomerular basement membrane, is one of the earliest, most consistent early signs of diabetes, and diabetic nephropathy is invariably associated with progressive proteinuria. Reductions of heparan sulfate in the basement membrane of retinal and renal capillaries also leads to the increased capillary permeability that occurs at both sites significantly contributing to diabetic retinopathy and nephropathy.
Glucose tolerance declines with age because of: 1) increased cell receptor resistance to insulin; 2) intracellular post receptor disturbances and 3) diminished pancreatic islet xcex2-cell sensitivity to insulin and glucose. Insulin resistance, with secondary hyperinsulinemia and/or hyperglycemia, contributes to many disorders associated with aging, i.e., hypertension, obesity, atherosclerosis, lipid abnormalities, coagulopathies and chronic metabolic perturbations including type 2 diabetes.
Although insulin resistance and type 2 diabetes each have an inherited pathogenic component, they both are substantially influenced by inappropriate diet and inadequate exercise.
In aging, as in diabetes, elevated circulating glucose reacts nonenzymatically with proteins and nucleic acids to form products that: 1) disturb the functionality of the cellular phospholipid membrane; 2) diminish tissue elasticity and 3) secondary to free radical formation, increase lipid peroxidation.
The ingestion of sugars, fats, and sodium has been linked to insulin resistance, while caloric restriction, exercise, ingestion of chromium, vanadium, magnesium, and certain antioxidants are associated with greater insulin sensitivity. Lifespan may favorably be affected, and the incidence of many chronic disorders commonly associated both with aging and with diabetes can be reduced, by manipulating the diet and its influence upon the glucose/insulin system.
Diabetesxe2x80x94Pertinent Anatomy and Physiology of Glucose Metabolism
The pancreas functionally integrates its exocrine and endocrine domains to modulate the kinetics and dynamics of intermediary metabolism:
1. Exocrine acinar cells produce amylase, which breaks down complex carbohydrates to monosaccharides in the intestine for absorption.
2. Endocrine islet xcex1- and xcex2-cells produce insulin, glucagon and somatostatin which regulate glucose production and utilization.
Glucose homeostasis requires a modulated endocrine system capable of controlling glucose flux into and out of the extracellular space. Insulin (xcex2-cells) and glucagon (xcex1-cells) must maintain a balance between glucose production, intracellular translocation and glucose utilization in the liver, adipose, muscle and neuronal tissue.
Failure of this integration between the exocrine and endocrine pancreatic functions is evident in diabetics: there is a loss of autocorrectionxe2x80x94i.e., although exocrine acinar amylase mRNA may decrease, endocrine-produced insulin normally reverses this, causing a corrective increase in acinar mRNA and amylase production.
Insulin
Insulin is synthesized from a very large physiologically inactive polypeptide, proinsulin, which is derived from a still larger polypeptide, preproinsulin. Insulin itself is a large, dual-chain polypeptide with, respectively, 21 and 30 amino acids in the A and B chains. The A and B chains of the dimer are linked by disulfide bonds and then complexed with zinc (Zn2+) for storage in the pancreatic xcex2-cells.
Insulin is released from xcex2-cells in response to elevated glucose levels. Under conditions of marked hyperglycemia, proinsulin is released in addition to insulin. Because of its slower disappearance, proinsulin may represent as much as 50% of the measured circulating xe2x80x9cinsulinxe2x80x9d in persons with hyperglycemia. If hyperglycemia is sustained, the continued overproduction of inactive proinsulin may exhaust xcex2-cells as they attempt to respond. This ultimately results in reduced insulin production. Moreover, the xe2x80x9cnumbingxe2x80x9d (or progressive reduction in the response) of xcex2-cells to the small amount of insulin that is present may ultimately lead to clinically overt type 2 diabetes and its more serious, often devastating complications. (See below.)
In addition to maintaining glucose translocation into cells, insulin stimulates cellular uptake of potassium and ascorbate. Thus, when combined with the usual hypomagnesmia of diabetes, insulin deficiency exaggerates or cause hypertension and the xe2x80x9ctissue scurvyxe2x80x9d commonly associated with type 2 diabetes.
Caveolar Insulin Transport
Most hydrophilic cell signaling substances like insulin have difficulty crossing cell membranes to institute intracellular effects. Instead, signal transduction to the inside of the cell occurs at caveolaexe2x80x94clusters of receptors located in specialized areas of the cell membrane. Caveolae, in fact, are membrane systems responsible for signal transduction and facilitating the integration of nutritional, mechanical and humoral information at the cell surface. Rich in phospholipids, cholesterol and lipid-anchored membrane proteins, they present as coherent patches immersed in the lipid bilayer, like floating icebergs in the sea. Resident molecules move through endocytotic/exocytotic caveolar compartments. Caveolae and other similarly functional glycolipid rafts are especially abundant in the cellular membranes of insulin-sensitive cells.
Although many different signaling molecules may be available, the caveolae are the major sites for the integration of cellular signalling. Integration in this context refers to the interplay of two or more signaling processes that result in reciprocal modulation. In the treatment of type 2 diabetes, the ability of caveolae to sequester molecules provides a target for influencing both imported and locally produced molecules in the modulation of cellular signaling.
Within caveolae, glycosylphosphatidylinositol (GPI) proteins transfer information between different membrane compartments. In particular caveolin-1, an insulin receptor, interacts with these GPI proteins permitting insulin translocation. (See GLUT4, below.)
Three types of receptor proteins are located within the caveolae of cell membranes:
Type I receptors have enzyme activity and usually possess an intracellular phosphotyrosine kinase (PTK) domain. Once the domain is activated by a ligand, e.g., insulin, PTK phosphorylates the intracellular tyrosine present in multiple proteins. These proteins then bind to phosphorylated tyrosine receptors of caveolin-1 (either to the insulin receptor itself or complexed with it) and a cascade of signalling proceeds to other parts of the cell.
Type II receptors are ion channels. Here, binding with a ligand, e.g., acetylcholine, causes rapid opening of an ion channel within the membrane protein permitting passage of selected ions: Na+, K+ or Clxe2x88x92.
Type III receptors as a class are referred to as G (guanine nucleotide) proteins. These are 7-helix transmembrane proteins that transfer their signal via a complex intracellular second messenger system. These receptors only recently have had their structure completely defined.
Once insulin is bound to Type I caveolin-1 receptors and initiates phosphorylation of the intracellular tyrosine domain, the resulting phosphorylation cascade activates GLUT4 vesicles. These fuse to the plasma membrane and proceed to translocate glucose into the cell. This activation and fusion require interaction between GLUT4 vesicle protein and cell membrane protein Syntaxin 4 (S4). As long as S4 is complexed with the cell membrane protein Synip, GLUT4 vesicles are inactive. Insulin dissociates the Synip:S4 complex, frees S4 to bind with GLUT4 vesicles and vesicle translocation of glucose into the cell becomes possible. Synip is the primary insulin regulated protein directly involved in glucose transport and GLUT4 vesicle translocation. It should be noted here that the antihyperglycemic effect of the trace element vanadium may in part be due to direct activation of the insulin receptor and in part to a prolongation of the action of insulin, possibly by inhibiting the formation of this Synip:S4 complex.
Complex spatial compartmentalization is involved in the specificity of insulin action. As examples:
Once it is complexed, the insulin-activated receptor (caveolin-1) within the caveola is itself translocated endocytotically into the cytoplasm where its passenger insulin is released.
In addition to dissociating the Synip:S4 complex, insulin also activates xe2x80x9cprotein targeting for glycogenxe2x80x9d (PTG) which forms a distinct insulin pool of protein phosphatase 1 (PP 1). This is complexed with enzymes regulating a dephosphorylation cascade leading to the production and storage of glycogen. The insulin receptor is then exocytotically translocated to a position within a caveola of the cell membrane, under control of a feedback mechanism.
Caveolae are sensitive to lipids, especially cholesterol, and contain receptors that bind HDL, LDL and oxidized lipoproteins (oxLDL). The presence of elevated levels of oxLDL adversely affect caveolar efficiencies. (See, below.)
Disruption of these functions can have unexpected consequences given their involvement not only in insulin cell signaling but also in calcium (Ca2+) metabolism, blood clotting and cholesterol transport.
Confounding any understanding of these already intricate, interrelated facets of insulin functionality are the varieties of its actions according to cell type, dosage, time of dosage and the presence of other hormones. And to make things even more complicated, insulin may initiate either phosphorylation or dephosphorylation cascades within the cell. Although the insulin receptor itself is phosphorylated in its tyrosine domain (as noted above), the subsequent changes in protein phosphorylation occur predominantly on serine and threonine residues and, in addition, L-arginine supports ligand binding to phosphotyrosine receptors, including the insulin receptor.
Many steps in these phosphorylation cascades involve ATPase, which is dependent on magnesium Mg2+ as a cofactor. Mg2+ deficiency is sufficiently common in diabetics that its oral supplementation is recommended by the American Diabetes Association for diabetics with normal renal function.
OxLDL (which is increased by both hyperinsulinemia and hyperglycemia) displaces cholesterol from the caveolae, driving endothelial nitric-oxide synthase (eNOS) from caveolae and impairing its activation: Vasoconstriction and increased coaguability arise from this destabilization of the physiological balance between the vasodilation of NO, the vasoconstriction of ET-1 and the availability of cGMP. Although HDL helpfully reduces the ability of oxLDL to decrease eNOS activation (and thus preserves subcellular levels of eNOS and indirectly NO), the level of HDL is reduced in patients with insulin resistance.
Mitochondria and Pancreatic xcex2-Cell Apoptosis
Pancreatic xcex2-cell apoptosis is responsible for irreversible progression toward insulin dependence in type 2 diabetes.
Apoptosis is an enzyme driven catabolic cell-death process. Activation of endonucleases and specific proteases (caspases) occurs when mitochondria make a xe2x80x9cdecision to diexe2x80x9d. Inhibition of endonucleases and caspases do not prevent apoptosis, indicating that that the xe2x80x9cdecision to diexe2x80x9d is taken before catabolic enzymes are activated and that the activation of these enzymes is by-product of the cell-death process and not a regulatory event.
The sequence leading to apoptosis is: 1) A pre-mitochondrial (induction) phase, in which numerous physiological and some pathological stimuli (e.g., prooxidants, increased cytosolic Ca2+, induced NO) trigger an increase in mitochondrial membrane permeability. 2) A mitochondrial (effector) phase during which mitochondrial membrane integrity is lost and the xe2x80x9cdecision to diexe2x80x9d is made. 3) A post-mitochondrial (degradation) phase during which intermembrane proteins (cytochrome C, apoptosis-inducing factor) are released which activate catabolic hydrolases (e.g., endonucleases, caspases) responsible for apoptotic degradation of essential proteins and nuclear DNA. This invention reduces the pathologic stimuli of the induction phase of apoptosis, including that of the pancreatic xcex2-cell.
Not unexpectedly, the complexity of the involved pathophysiologies defines their nonlinearity. This complexity also emphasizes the necessity for modulation at the many points of potential instability in these processes. The inadequacy or lack of such modulation at multiple points may eventually lead to overt type 2 diabetes itself. The identification and influence of these modulation points represent therapeutic opportunities and underly the rationale of this invention.
Pertinent Pathophysiology of Diabetic Mellitus
In normal subjects, after an overnight fast, glucose is produced from hepatic glycogen (25%) and gluconeogenesis (75%): The kidney, in addition to the liver, is capable of gluconeogenesis. The main gluconeogenic precursors for the liver are amino acids (predominantly alanine and glutamine derived from muscle protein) and glycerol from triglyceride hydrolysis in adipose tissue. Catecholamines stimulate gluconeogenesis, as does glucagon via cAMP, while cortisol has a delayed effect in causing hyperglycemia. Insulin opposes these gluconeogenic and glycogenolytic actions.
Hepatic glucose production can be autoregulated according to portal vein glucose levels, assuming there is a normal response to insulin.
As previously stated, the initial event in insulin action is its binding to an enzymatic caveolar receptor. This causes a conformational change in the intracellular tyrosine kinase domain of the receptor, its autophosphorylation and an intracellular phosphorylation cascade that mediates some of insulin""s effects. After caveolin-1 binding occurs, the resulting insulin-receptor complex is internalized endocytotically and insulin dissociates intracellularly. Some residual receptors simply degrade, some pass to the Golgi apparatus to join others, newly synthesized, and are recycled exocytotically to a caveolar membrane region to await another insulin ligand.
In persistent hyperglycemia the turnover of receptor binding and internalization are increased resulting in a net reduction in the number of available receptors at the cell membrane (downregulation). As more and more receptors are occupied, adjacent unoccupied receptors become less receptive (negative co-operativity). Downregulation and negative co-operativity combine to decrease insulin effectiveness during sustained hyperglycemia. Thus, sustained hyperglycemia results in decreased insulin receptivity and increased insulin resistance.
Although circulating insulin levels are frequently elevated early in type 2 diabetes, a deficiency of intracellular insulin and increased cellular resistance to many of insulin""s actions simultaneously occur: there is resistance to the stimulation of glucose uptake by muscle and liver, there is resistance to the suppression by insulin of hepatic glucose production, there is resistance to the suppression by insulin of lipolysis in adipose tissue, etc. Several possibilities for these inadequacies have been postulated: 1) that there is some structural abnormality in the insulin receptor or in the region of the caveolin-1 insulin receptor, which results in disruption of the intracellular phosphorylation cascade; or 2) that there is an abnormality in the endocytotically intracellular insulin release effecting glycogenic enzymes; or 3) that there is a Synip related effect. All three probably contribute to insulin resistance. Again, the process is unclear, complex and nonlinear.
Recent research suggests that there is a high expression of the cytokine tumor necrosis factor-xcex1 (TNF-xcex1) in the adipocytes of obese individuals, and that this TNF-xcex1 is a principal contributor to insulin resistance and subsequent type 2 diabetes in obese patients. TNF-xcex1 is an important regulator of the processes of apoptosis and thus modulates the volume of tumor, adipose and muscular tissues. It is produced not only by immunocompetent cells but also by adipocytes and muscle cells. This cytokine is activated in tumors and obesity, among other conditions. TNF-xcex1 promotes insulin resistance and anorexia, by acting on the phosphorylation of IRS-1 and PI-3 kinase, by modifying resistance through regulation of the synthesis of the insulin responsive glucose transporter GLUT4, and through interference with insulin signaling (perhaps via leptin).
Studies conducted on obese human patients have demonstrated a correlation between levels of TNF-xcex1, the extent of obesity, as well as the level of hyperinsulinemia (the results of one recent study are consistent with the hypothesis that TNF-xcex1 could be involved in the regulation of plasma leptin concentrations in obese subjects).
Irrespective of the cause, insulin resistance is associated with widespread and adverse effects on health. This is true even when glucose tolerance is only mildly impaired but not yet in the overt diabetic range. Notable among the adverse effects is the predisposition to vascular disease affecting large blood vessels and an association with hypertension and dyslipidemia (elevated triglycerides and decreased HDL). In fact, this combination of 1) glucose intolerance, 2) insulin resistance, 3) hypertension and 4) dyslipidemia is common enough to have acquired the name Syndrome X, the insulin resistance syndrome or Reaven""s syndrome. Clinically it defines hundreds of millions of people worldwide.
It is clear that the process governing both insulin resistance and type 2 diabetes is diagrammatically syncytial. It is not a linear, straightforward process that lends itself to a single treatment modality. Neither disease is a singularity and the pathophysiologic continuum of each is not rationally approachable with a single pharmaceutical xe2x80x9csilver bulletxe2x80x9d.
Aging and Diabetes Mellitus
With aging there is a gradual decline in glucose tolerance at least in part because of a progressively increased resistance to insulin at its receptor site and a decreased response by the pancreatic xcex2-cells to glucose levels. In aging, similar to diabetes, the elevated circulating glucose secondary to increasing insulin resistance reacts nonenzymatically with proteins and nucleic acids to form products that disturb cell membrane function and diminish tissue elasticity. Also, these disturbances in glucose/insulin metabolism are associated with increased lipid peroxidation from elevated free radical formation resulting from the autooxidation of glucose. Augmented free radical formation and lipid peroxidation, common in diabetes mellitus, are associated with the xe2x80x9cpremature agingxe2x80x9d of diabetic patients. Long term, excessive ingestion of sugars, fats and sodium have been linked to decreased insulin sensitivity, while caloric restriction, exercise, ingestion of chromium, vanadium, Mg2+, certain free radical scavengers and nuclear factor kappa B (NFkappaB) inhibitors are associated with greater insulin sensitivity. Thus, manipulation of the diet by influencing the glucose/insulin system may favorably affect lifespan and reduce the incidence of the microvascular and macrovascular complications of type 2 diabetes.
Vascular Pathology
The earliest microvascular lesion of diabetes is a variable thickness of the basement membrane. A healthy basement membrane provides vascular stability and importantly, a permeability barrier. Cellular impermeability requires a negative electrical charge provided by heparan sulfate, a polyanionic proteoglycan. Sulfate groups provided by lipoic acid, n-acetylcysteine (NAC) and possibly taurine, may contribute to the adequacy of this necessary negativity of the cell membrane. In diabetes both the basement membrane thickness and heparan sulfate levels are decreased. As a result, vessel permeability is increased. Increased vessel permeability is the most notable initial microvascular complication in diabetes.
Early in diabetes there are additional abnormal microvascular (arteriolar and capillary) dysfunctions: e.g., intraluminal pressure and flow are both increased: these changes, plus the increased permeability of the basement membrane and the associated vascular endothelial dysfunction, limit normal vascular autoregulatory mechanisms. This combination of failures leads to the familiar diabetic clinical manifestations of microvascular and macrovascular insufficiencies of the heart, extremities, kidney, eye and brain.
Microvascular complications
1. Diabetic retinopathy is the leading cause of blindness in the working population.
2. Diabetic nephropathy is common in type 2 diabetes. Risk of death is increased 100 fold.
3. Diabetic neuropathy increases each decade to a 60% incidence after 25 years.
Macrovascular complications
1. Cardiovascular risk of death is increased three fold.
2. Cerebrovascular risk of death is increased.
3. Amputation risk is increased five fold.
Biochemical Mechanisms of Diabetic Complications
Free Radical Damage
Release of cytochrome C from dysfunctional mitochondria
Non-enzymatic glycation
Lipoprotein modifications
Disturbances of physiological NO effects
Sorbitol and myoinositol metabolic abnormalities
Interference with proteoglycans
Although diabetes mellitus and insulin resistance are progressive, complex and frequently unpredictable processes with many points of potential instability, the latter are identifiable. To have any long-term chance of favorably influencing the cellular pathophysiology of insulin resistance and type 2 diabetes, any clinical approach must involve not only the coordination of life style modification, but also utilize finely calibrated combinations of pharmaceutical agents acting at multiple biomolecular nodes of modulation.
Therefore it is useful to consider, in turn, the pathologic states caused by insulin resistance and type 2 diabetes, the underlying molecular biologic defects or deficiencies, the existing modalities for favorably modulating these and the complementary, beneficial interactions of some of these approaches.
A. Pathologic States Caused by or Worsened by Insulin Resistance and/or Type 2 Diabetes
SPECIFIC: MICROVASCULAR COMPLICATIONS
1. NEPHROPATHY
2. NEUROPATHY
3. RETINOPATHY
NON-SPECIFIC: MACROVASCULAR COMPLICATIONS
1. ATHEROSCLEROSIS
2. HYPERTENSION
3. CORONARY ARTERY DISEASE
4. CEREBROVASCULAR DISEASE
5. PERIPHERAL VASCULAR DISEASE
RELATED MORBIDITY
1. OBESITY
2. POOR RESISTANCE TO INFECTION
3. PREMATURE AGING
4. CATARACTS
5. ALZHEIMER""S DISEASE (POSSIBLE)
B. Cellular Physiological and Molecular Biological Disturbances in Insulin Resistance and/or Type 2 Diabetes
1. INSULIN SENSITIVITY IS DECREASED
2. INSULIN RESISTANCE IS INCREASED
3. DURATION OF INSULIN ACTION IS DECREASED
4. HYPERINSULINEMIA
5. xcex2-CELL INSULIN SECRETION IS INITIALLY INCREASED, THEN DECREASED
6. xcex2-CELL DYSFUNCTIONAL APOPTOSIS
7. xcex2-CELL SENSITIVITY IS DECREASED
8. HYPERGLYCEMIA
9. ADVANCED GLYCATION PRODUCTS (AGEs) OCCUR
10. GLUCOSE AUTOOXIDATION OCCURS WITH FORMATION OF ROS (OXIDATIVE STRESS)
11. FREE RADICALS ARE INCREASED
12. GLUTATHIONE (GSH) EFFECTS ARE DECREASED
13. ENDOTHELIUM BECOMES DYSFUNCTIONAL
14. VASOCONSTRICTION IS INCREASED
15. DEFECTIVE ACETYLCHOLINE (ACH) RESPONSExe2x86x92VASOCONSTRICTION
16. SYMPATHETIC NERVOUS SYSTEM ENHANCED: NOCTURNAL HEART RATE INCREASED
17. CALCIUM SIGNALING IS DISTURBED
18. REDUCED eNOSxe2x86x92IMPAIRED VASODILATION
19. ET-1 IS INCREASED WITH INTENSE, PROLONGED VASOCONSTRICTION
20. VASCULAR SMOOTH MUSCLE (VSMC) HYPERTROPHY RESULTS
21. VCAM-1 and ICAM-1 (VASCULAR ADHESION MOLECULES) INCREASE
22. DESTABILIZATION OF PLATELETS
23. REDUCED SYNTHESIS OF HEPARAN SULFATE WITH PROTEINURIA
24. SECONDARY ELEVATION OF HOMOCYSTEINE
25. HOMOCYSTEINE AGGRAVATION OF DIABETIC HYPERTENSION and ATHEROGENESIS
26. VITAMIN Cxe2x86x92DEHYDRO ASCORBIC ACID (DHAA) IMBALANCE OCCURS
27. VITAMIN C MAY BECOME A PROOXIDANT
28. EXHAUSTION OF VITAMIN E
29. CELL MEMBRANE LIPID PEROXIDATION
30. DESTABILIZATION OF CELLULAR AND SERUM LIPIDS
31. DESTABILIZATION OF MEMBRANE CAVEOLAE
32. LDL OXIDATION
33. MACROPHAGE ACTIVITY INCREASED (FOAM CELL DEVELOPMENT)
34. ALDOSE REDUCTASE IS UNINHIBITED RESULTING IN INCREASED SORBITOL
35. POLYOL OSMOTIC EFFECT IS INCREASED
36. MYOINOSITOL AND TAURINE OSMOLAR EFFECTS ARE DISTURBED
37. STRUCTURAL AND FUNCTIONAL PERICYTE AND NEURONAL DISRUPTION
38. MICROVASCULAR BLOOD FLOW IS REDUCED
39. NERVE CONDUCTION VELOCITY IS DECREASED
40. HYPOMAGNESEMIA OCCURS, DECREASING INSULIN EFFECTxe2x86x92CELL MALFUNCTIONS
41. POSSIBLE DIABETIC ADVANCEMENT OF ALZHEIMER""S DISEASE
Oral Hypoglycemic Agentsxe2x80x94Aspects of Biochemistry
There are various pharmacological approaches to improving glucose homeostasis, but those currently used in clinical practice, either do not succeed in restoring normoglycemia in most patients, fail after a variable period of time or have side effects that ultimately preclude their use in many patients. The components of this invention will improve the performance, duration of effectiveness and safety of therapies, which depend upon the inclusion of the biguanides (e.g., metformin), of the sulfonylureas (various) or of sulfonylurea-biguanide combinations.
For glycemic regulation, four classes of oral drugs are currently available: biguanides (e.g., metformin), sulfonylureas (e.g., tolbutamide, glyburide, glipizide and others),xcex1-glucosidase inhibitors (e.g., acarbose and miglitol) and thiazolidinediones (e.g., troglitazone and rosiglitazone), each of these has a different mode and site of action.
This invention focuses on formulations containing multiple active ingredients in addition to a biguanide and/or a sulfonylurea for patients requiring a biguanide, one of the sulfonylureas or the concurrent use of both (i.e., a combination of sulfonylurea and biguanide) for treatment of progressive insulin resistance and type 2 diabetes.
The principle of long-term maintenance of glucose control applies to both progressive insulin resistance and type 2 diabetes. The treatment strategies while similar, are somewhat different. Progressive insulin resistance has as its central abnormality hyperinsulinemia. The latter persists as the disease progresses to type 2 diabetes with its central abnormality, hyperglycemia. In each case the process is nonlinear and its pharmacological modulation is complex.
A. Sulfonylureas
A.1. Sulfonylurea: Pharmacodynamics and Pharmacokinetics
The sulfonylurea group has dominated oral antidiabetic treatment for years. They primarily increase insulin secretion. Their action is initiated by binding to and closing a specific sulfonylurea receptor (an ATP-sensitive K+ channel) on pancreatic xcex2-cells. This closure decreases K+ influx, leading to depolarization of the membrane and activation of a voltage-dependent Ca2+ channel. The resulting increased Ca2+ flux into the xcex2-cell, activates a cytoskeletal system that causes translocation of insulin to the cell surface and its extrusion by exocytosis.
The proximal step in this sulfonylurea signal transduction is the binding to (and closure) of high-affinity protein receptors in the xcex2-cell membrane. There are both high and low-affinity sulfonylurea receptor populations. Sulfonylurea binding to the high-affinity sites affects primarily K(ATP) channel activity, while interaction with the low-affinity sites inhibits both Na/K-ATPase and K(ATP) channel activities. The potent second-generation sulfonylureas, glyburide and glipizide, are able to saturate receptors in low nM concentration ranges, whereas older, first-generation drugs bind to and saturate receptors in microM ranges.
The association of sulfonylurea receptors (SURs) with K(IR)6.x subunits to form ATP-sensitive K+ channels, presents perhaps the most unusual function known for members of the transport ATPase family. The integration of these two protein subunits extends well beyond conferring sensitivity to sulfonylureas. These SUR-K(IR)6.x interactions are critical for all of the properties associated with native K(ATP) channels including quality control over surface expression, channel kinetics, inhibition and stimulation by magnesium nucleotides and response both to channel blockers like sulfonylureas and to potassium channel openers. The K(ATP) channel is a unique example of the physiologic and medical importance of a transport ATPase and provides a paradigm for how other metallic members of the family may interact with other ion channels. This also speaks to the importance and the mechanism of modulation by Mg2+ of many aspects of membrane channel receptors.
The activity of ATP-sensitive K+ channels is also controlled by insulin secretagogues, by glucose and by certain amino acids such as cationic L-arginine and the non-polar, essential amino acid L-leucine. The amino acid secretagogues must be metabolized to inhibit the K+ channel activity and appear to do so by increasing the level of ATP, or by increasing the ATP/adenosine diphosphate (ADP) ratio. As a result, the increased availability of ATP reduces channel activity by binding to a specific site on the cytoplasmic surface of the receptor protein. To function as an insulin secretagogue, L-arginine requires adequate thiamine and L-leucine requires thiamine for its catabolic metabolism as well. This invention will enhance the effectiveness of sulfonylureas by supplying complementary amino acid secretagogues in a complementary milieu.
There is a synergy between the action of glucose and that of the sulfonylureas: sulfonylureas are better effectors of insulin secretion in the presence of glucose. For that reason, the higher the level of plasma glucose at the time of initiation of sulfonylurea treatment, the greater the reduction of hyperglycemia.
Exposure of perfused rat hearts to the second-generation sulfonylurea glyburide leads to a dramatic increase in glycolytic flux and lactate production. When insulin is included in the buffer, the response to glyburide is significantly increased. (Similarly, glyburide potentiates the metabolic effects of insulin.) Because glyburide does not promote glycogenolysis, this increase in glycolytic flux is caused solely by a rise in glucose utilization. Since the drug does not alter oxygen consumption, the contribution of glucose to overall ATP production rises while that of fatty acids falls. These metabolic changes aid the heart in resisting ischemic insults.
Insulin, on the other hand, is released by the pancreas into the portal vein, where the resultant hyperinsulinemia suppresses hepatic glucose production and the elevated level of arterial insulin enhances muscle glucose uptake, leading to a reduction in postprandial plasma glucose levels.
The initial hypoglycemic effect of sulfonylureas results from increased circulating insulin levels secondary to the stimulation of insulin release from pancreatic xcex2-cells and, perhaps to a lesser extent, from a reduction in its hepatic clearance. Unfortunately, these initial increases in plasma insulin levels and xcex2-cell responses to oral glucose are not sustained during chronic sulfonylurea therapy. After a few months, plasma insulin levels decline to those that existed before treatment, even though reduced glucose levels are maintained. Because of downregulation of xcex2-cell membrane receptors for sulfonylurea, its chronic use results in a reduction in the insulin stimulation usually recorded following acute administration of these drugs. More globally, impairment of even proinsulin biosynthesis and, in some instances, inhibition of nutrient-stimulated insulin secretion may follow chronic (greater than several months) administration of any of the sulfonylureas. (However, the initial view that the proinsulin/insulin ratio is reduced by sulfonylurea treatment seems unlikely in light of recent research.) If chronic sulfonylurea therapy is discontinued, a more sensitive pancreatic xcex2-cell responsiveness to acute administration of the drug is restored.
It is probable that this long-term sulfonylurea failure results from chronically lowered plasma glucose levels (and a resulting feedback reduction of sulfonylurea stimulation); it does, however, lead to a diminishment of the vicious hyperglycemia-hyperinsulinemia cycle of glucose toxicity. As a result, the sulfonylureas reduce nonenzymatic glycation of cellular proteins and the association of the latter with an increased generation of advanced glycation end products (AGEs), and improve insulin sensitivity at the target tissues. But, it should be kept in mind that one of these cellular proteins is insulin, which is readily glycated within pancreatic xcex2-cells and under these conditions, when it is secreted it presumably is now ineffective as a ligand.
The formulations of this invention reduce protein glycation and will thereby increase the amount of secreted insulin that is effective at the target tissues.
It has been suggested that sulfonylureas may have a direct effect in reducing insulin resistance on peripheral tissues. However, most investigators believe that whatever small improvement in insulin action is observed during sulfonylurea treatment is indirect, possibly explained (as above) by the lessening of glucose toxicity and/or by decreasing the amount of ineffective, glycated insulin.
When sulfonylurea treatment is compared with insulin treatment it is found that: (1) treatment with sulfonylurea or insulin results in equal improvement in glycemia and insulin sensitivity, (2) the levels of proinsulin and plasminogen activator inhibitor-1 (PAI-1) antigen and its activity are higher with sulfonylurea, and (3) there are no differences in lipid concentrations between therapies.
Because sulfonylureas (glyburide) are weak acids they are more than 98% bound to albumin, but this does not appear to be influenced by the extent of albumin glycation.
A.2. Sulfonylurea: Effectiveness
The hypoglycemic potency of sulfonylureas is directly related to the starting fasting plasma glucose level. The higher the fasting plasma glucose level, the greater its decrease when treated with sulfonylureas. In the United States, the mean HbA1C value in diabetic patients is 10%, which corresponds to a fasting plasma glucose level of more than 200 mg/dL. In such patients treated with sulfonylureas, one can expect the fasting plasma glucose level to decrease by 60 to 70 mg/dL and the HbA1C value to decrease by 1.5 to 2.0 percentage points. Approximately 25% of type 2 diabetics treated with a sulfonylurea will achieve a fasting plasma glucose level lower than 140 mg/dL. However this also means that 75% will not reach this goal, and thus will require some type of additional therapy.
In some type 2 diabetics, autoantibodies to islet-cell cytoplasm (ICA) and glutamic acid decarboxylase (GADA) can occur. The phenotype of older adults is similar to type 2 diabetics without antibodies, and the occurrence of these antibodies predicts an increased likelihood of insulin treatment because of progressive xcex2-cell loss. Signs of islet cell autoimmunity occur in 12% of type 2 diabetics over the age of 65.
In addition, there is an increase in fibrinogen (P=0.005) and C-reactive protein levels (P=0.025) in type 2 diabetic patients with autoantibodies. A pronounced activation of the acute-phase response, found to be associated with islet cell autoimmunity, may in part explain the associated defects in insulin secretion. This not only has direct implications for adequate classification and treatment of type 2 diabetes in the elderly, but also for understanding the autoimmune/inflammatory mechanisms involved in the pathogenesis of hyperglycemia.
By reducing dysfunctional xcex2-cell apoptosis, this invention will enhance the effectiveness of sulfonylurea therapy by stopping or slowing the progression of type 2 diabetes toward this stage of progressive autoimmune/inflammatory xcex2-cell destructionxe2x80x94sometimes referred to as xe2x80x9ctype 1.5xe2x80x9d diabetes.
Of those patients who have a good initial response to sulfonylurea therapy, the secondary failure rate is about 5% to 7% per year. After 10 years this failure has mounted to over 50% and most sulfonylurea-treated patients require a second oral agent. Less than 20% of type 2 diabetics have satisfactory long-term therapy after 10 years of sulfonylurea treatment. First and second generation sulfonylureas are equally subject to secondary failure. Switching from a first to a second-generation sulfonylurea has been more or less equally xe2x80x9csuccessfulxe2x80x9d, but ultimately treatment is unsatisfactory. It is the intention of this invention to extend the duration of effect of sulfonylurea treatment of type 2 diabetes by delaying the onset, and slowing the progression of xcex2-cell dysfunction and inappropriate xcex2-cell apoptosis.
All sulfonylureas fail at rates that are dependent both on the phenotype at presentation and (perhaps) on the agent used initially. Higher eventual failure rates are found in those with higher initial glucose concentrations, those who are younger, those with lower xcex2-cell reserve and in the United Kingdom Prospective Diabetes Study (UKPDS) those randomized to second generation drugs, compared with first generation drugs. Prospective placebo-controlled trials have shown that second generation sulfonylureas (glipizide, glyburide, and glimepiride) exert equipotent glucose-lowering effects, but it is not known whether they also differ in their therapeutic end results.
Regarding the benefit of intensive therapy with sulfonylureas (chlorpropamide, glibenclamide) or with insulin in type 2 diabetes, the UKPDS interpreted their data to indicate that xe2x80x9c. . . intensive blood glucose control by either of the sulfonylureas or by insulin, substantially decreases the risk of microvascular complications, but not macrovascular disease . . .xe2x80x9d.
Management of patients with progressive insulin resistance and type 2 diabetes should focus on decreasing the excess macrovascular disease with which these are associated, as well as preventing or minimizing microvascular disease. As shown by the UKPDS data, near-normoglycemic control can reduce microvascular disease. However, this requires the concomitant management of the cardiovascular risk factors of the insulin resistance syndrome associated with type 2 diabetes: e.g., a reduction of the macrovascular-disease-promoting sulfonylurea side effect of carnitine depletion and/or a reduction of metformin-induced hyperhomocysteinemia.
The formulations of the invention will enhance the microvascular benefits associated with the sulfonylureas. In addition, by rectifying the adverse side effects of sulfonylurea treatment, and by modifying the adverse components of the insulin resistance syndrome, the invention will decrease the risk of macrovascular disease.
If combined with caloric dietary regulation, rapid- and short-acting sulfonylureas may help patients reach and maintain euglycemia without provoking chronic hyperinsulinemia or weight increase. There is no evidence that sulfonylurea treatment causes xcex2-cell exhaustion; instead, the antihyperglycemic effect helps improve xcex2-cell function. Sulfonylurea xe2x80x9cfailuresxe2x80x9d are often dietary failures or due to late introduction of these drugs, i.e., when xcex2-cell function is already attenuated. Desensitization of the insulinotropic effect of sulfonylureas may occur, but might be avoided by discontinuous (less than 24 h/day) sulfonylurea exposure, i.e., once-daily administration of a short-acting sulfonylurea in a moderate dose. That is, the failure rate seems to dose related. The invention will permit the clinician more latitude in adjusting downward the dosage of a prescribed sulfonylurea, and it will permit xe2x80x9cpulsingxe2x80x9d of the latter and avoid desensitization. Furthermore, it will provide the luxury of a safe delay of use of the because of a prophylactic prolongation of improved xcex2-cell function: this delay in the use of the sulfonylureas will delay the onset of their failure. It is not expected that it will eliminate entirely ultimate failure.
A.3. Sulfonylurea: Additional Beneficial Effects
Type 2 diabetes mellitus is part of a complicated metabolic-cardiovascular pathophysiologic cluster alternately referred to as the insulin resistance syndrome, Reaven""s syndrome, the metabolic syndrome or syndrome X. Since the macrovascular coronary artery disease associated with insulin resistance and type 2 diabetes is the major cause of death in the latter, it is desirable that any hypoglycemic agent favorably influences known cardiovascular risk factors. But the results in this area have been only mildly encouraging. This invention will add a cardiovascular risk reduction dimension to syulfonylurea therapy.
Sulfonylureas have been reported to have a neutral or just slightly beneficial effect on plasma lipid levels: plasma triglyceride levels decrease modestly in some studies. This hypolipidemic effect probably results from both a direct effect of sulfonylurea on the metabolism of very-low-density lipoprotein (VLDL) and an indirect effect of sulfonylurea secondary to its reduction of plasma glucose levels.
It has been shown the sulfonylurea gliclazide (but not necessarily another oral hypoglycemic) reduces platelet aggregation and has a beneficial effect on the fibrinolytic system. As a group, the sulfonylureas decrease vessel permeability in a manner that is independent of their hypoglycemic properties. These additional actions may be useful in preventing or attenuating the long-term vascular complications of diabetes, e.g., diabetic retinopathy. While the favorable effect of reducing platelet aggregation seems established, a disturbing recent study shows an increase in PAI-1 in chronically treated sulfonylurea patients.
The formulations of this invention provide appropriate therapeutic levels of a sulfonylurea and will enhance and/or extend the beneficial effect of the sulfonylureas upon plasma lipids, coagulopathy and microvascular permeability.
A.4. Sulfonylurea: Adverse Effects
The most frequent adverse effect associated with sulfonylurea therapy is weight gain, which is also implicated as a cause of secondary drug failure.
Sulfonylureas frequently: (1) stimulate renal renin release; (2) inhibit renal carnitine resorption; (3) increase PAI-1; and (4) increase insulin resistance.
Renal effects from treatment with the sulfonylureas can be detrimental. Because the sulfonylureas are K(ATP) blockers they are diuretics although, fortunately, they do not produce kaliuresis. They may stimulate renin secretion from the kidney, initiating a cascade to angiotensin II in the vascular endothelium that results in vasoconstriction and elevated blood pressure.
They inhibit renal carnitine reuptake. This raises the question as to what role they play in the homeostasis of other amino acids for which deficiencies should be avoided in progressive insulin resistance and type 2 diabetes, e.g., taurine and L-arginine. Given these renal effects of the sulfonylureas, it is not surprising that there macrovascular benefits are not associated with their use. (See above.) Sulfonylureas, while reducing hyperglycemia, tend to intensify the insulin resistance syndrome: obesity, insulin resistance, hypertension, and coagulopathy. The formulations of this invention reduce this negative effect on the insulin resistance syndrome and the secondary amino acid deficiencies caused by the clinical use of sulfonylureas.
The kidney plays an important role in the homeostasis of carnitine, reabsorbing it almost completely from the glomerular filtrate. Carnitine is pivotal for the mitochondrial energy system to function efficiently. Its deficiency leads to reduced fatty acid oxidation and ATP production, both of which are important in avoiding weight gain and maintaining the effectiveness of nutrient insulin secretagogues. This invention improves sulfonylurea-induced inhibition of hepatic fatty acid oxidation and provides support for the production of ATP (necessary for physiologic pancreatic insulin production), thereby lessening the adverse weight gain secondary to sulfonylurea treatment and reducing the accumulation of fatty acid-derived free radicals.
Sulfonylurea treatment induces coronary vasoconstriction from K+ ATP-channel blockade, and thus reduces coronary blood flow at rest by about 25%. It does not reduce flow during exercise so long as the L-arginine-cNOS-NO-cGMP pathway is normal. The invention provides support for the cGMP pathway.
PAI-1 antigen and activity increase with sulfonylurea treatment compared to insulin, perhaps explaining, in part, the failure of prevention of macrovascular complications in spite of glycemic control.
Proinsulin levels may increase during sulfonylurea therapy.
The most discussed, important adverse effect of chronic sulfonylureas use is long lasting, significant hypoglycemia. The latter may lead to permanent neurological damage or even death, and is most commonly seen in elderly subjects who are exposed to some intercurrent event (e.g., acute energy deprivation) or to drug interactions (e.g., aspirin, alcohol). Long-lasting hypoglycemia is more common with the longer-acting sulfonylureas glyburide and chlorpropamide. For this reason sulfonylurea therapy should be maintained at the lowest possible dose. (Surprisingly, the dose-response relationships of the sulfonylureas have been poorly investigated.) By complementing and efficiently optimizing the therapeutic action of sulfonylurea, the formulations of this invention permit the use of minimal doses of sulfonylureas, thereby lowering the risks of sulfonylurea therapy, including hypoglycemia.
There is a greater suppression of hepatic glucose production with glyburide, which may explain the higher incidence of hypoglycemia seen with its use: mild hypoglycemic reactions occur in about 4% of patients, and severe hypoglycemic reactions requiring hospitalization have been stated to occur with a frequency of 0.4 cases per 1000 patient treatment years. The UKPDS reported a somewhat higher incidence.
In two surveys (1969 and 1984), all emergency wards in Switzerland reported on the incidence in their units of severe episodes of hypoglycemia during treatment with sulfonylureas. Each of these surveys referred to a ten-year period (period A 1960-1969, period B 1975-1984). The number of severe episodes of hypoglycemia reported was 78 for period A and 116 for period B. The incidence of fatalities from sulfonylurea hypoglycemia in these facilities was 6.5% in period A (1960-1969), and 4.3% in period B (1975-1984). Advanced age was a risk factor in hypoglycemia in these patients: 77% of patients with hypoglycemia were over 69 years of age, whereas only 50% of all diabetics treated with sulfonylurea preparations were in this age group. Further risk factors were impaired renal function (21%) and possible drug interactions (27%).
As our population ages and as the prevalence of xe2x80x98couch potatoesxe2x80x99 rises, the danger of sulfonylurea hypoglycemia continually increases. The formulations of this invention are of increasing importance, because they permit clinical reductions in sulfonylurea dose levels.
In patients with a reduced glomerular filtration rate, the risk of hypoglycemia is high, and therapy with sulfonylureas, which are renally excreted, should be avoided.
The various adverse, dose-related drug interactions that have been described (notably, aspirin and alcohol), are especially common with first-generation sulfonylureas.
The controversial results of the University Group Diabetes Program study (1970) suggested that sulfonylureas might exacerbate coronary artery disease in patients with type 2 diabetes. Subsequent clinical trials have not demonstrated these increased cardiac mortality rates in diabetic patients actually treated with sulfonylureas. In fact, the UKPDS found no increased incidence of coronary artery disease in those patients with type 2 diabetes, who were assigned to intensive therapy with sulfonylureas, when compared with patients receiving diet therapy. There is no published data to support an advantage of any one sulfonylurea with respect to coronary artery disease. An American Diabetes Association policy statement opposes any formal restrictions based on the interpretations of the University Group Diabetes Program findings.
A.5. Currently Available Sulfonylureas (USA)
Sulfonylureas are divided into first-generation and second-generation drugs. First-generation sulfonylureas have a lower binding affinity to the sulfonylurea receptor and require higher doses than second-generation sulfonylureas. Generally, therapy is initiated at the lowest effective dose and titrated upward every 1 to 4 weeks until a fasting plasma glucose level of 110 to 140 mg/dL is achieved. Most (75%) of the hypoglycemic action of the sulfonylurea occurs with a daily dose that is half of the maximally effective dose. If no hypoglycemic effect is observed with half of the maximally effective dose, it is unlikely that further dose increases will have a clinically significant effect on blood glucose level.
In summary, sulfonylureas are effective glucose-lowering drugs that work by stimulating insulin secretion. They have a beneficial effect on diabetic microangiopathy, but no appreciable beneficial effect on diabetic macroangiopathy. Weight gain is common with their use. Sulfonylureas may cause hypoglycemia, which can be severe, even fatal. They may reduce platelet aggregation and slightly increase fibrinolysis, perhaps indirectly. However they also may increase PAI-1. They have no direct effect on plasma lipids. They inhibit renal resorption of carnitine and may stimulate renal renin secretion. The sulfonylureas, especially generics, are inexpensive and are the oral antidiabetic drug of choice if cost is the major consideration. Sulfonylurea dosage can be minimized, therapeutic effect maximized, safety improved and the scope of beneficial effects broadened in progressive insulin resistance, insulin resistance syndrome and type 2 diabetes when delivered in the formulations of this invention.
A.6. Use of the Invention for the Prevention and Treatment of Insulin Resistance Syndrome and Type 2 Diabetes (Sulfonylurea+Other Active Ingredients)
As illustrated by the foregoing list of cellular physiological and molecular biological disturbances, both insulin resistance syndrome and type 2 diabetes are progressive, complex, dynamic metabolic system failures with potential instability at many points. Its genesis is in part related to the aging process and is in part a product of environment and lifestyle. Underlying it all is a genetic dimension, which is not singular in nature. Because there are so many points of physiologic instability, neither pathologic process will predictably respond in its entirety to a single treatment modality. Rather, it is more logical to provide a favorable physiologic milieu by identifying those multiple points where influence upon biochemical modulation may reasonably be brought to bear and to design multicomponent therapeutic formulations to target them concurrently. In this fashion the therapy will insure that molecular deficiencies or inadequacies do not trigger the system to respond nonlinearly to those stresses known to be detrimental to persons with the potential for developing (or who already have) insulin resistance or type 2 diabetes. This physiological modulation is achieved by the formulations of this invention and is the basis for their improvement in the therapeutic efficiency and safety of sulfonylureas.
As an individual progresses toward and into type 2 diabetes, an increasing number of specific complementary biomolecules, biofactors and trace elements are necessary to compliment sulfonylureas, as shown in the following illustrations. It should be pointed out that a xe2x80x9cshotgunxe2x80x9d approach that throws everything in the biochemical bible at insulin resistance or type 2 diabetes not only is illogical, unnecessary and expensive, but also may be detrimental. Errors of commission in this regard are as inappropriate as errors of omission.
The present invention resides in an oral dosage form of a pharmaceutical preparation, which contains, as one of its active ingredients, a sulfonylurea for use in the prevention and treatment of insulin resistance and/or type 2 diabetes. The preparation contains elements of specific, sometimes unique, therapeutic biomolecules, biofactors and trace elements selected because of their particular and critical, combinational physiological effects. These are formulated in amounts to achieve maximum complementarity of action with sulfonylureas. The formulations are designed to increase the efficiency and prolong the clinical period of use of the sulfonylurea, which is included. In addition the formulations will reduce, delay or avoid side effects known to occur with the clinical use of sulfonylureas.
In the United States alone, 16 million people have type 2 diabetes and a substantial multiple, perhaps 4xc3x97 to 5xc3x97, are insulin resistantxe2x80x94at least one-half of these are undiagnosed. Type 2 diabetes is preceded by a long period of insulin resistance, impaired glucose tolerance and a reversible metabolic state associated with an increasing prevalence of macrovascular complications. At the time of diagnosis, long-term complications have already developed in almost one fourth of these patients, largely because of insulin resistance and its associated hyperinsulinemia and dyslipidemia.
Susceptibility to type 2 diabetes requires both genetic (most likely polygenic) and acquired factors. Its continuing pathogenesis involves an interplay of progressive cellular insulin resistance and pancreatic xcex2-cell failure. Any ideal treatment of type 2 diabetes must reduce insulin resistance and xcex2-cell dysfunction in a majority of treated patients and prevent, delay, or reverse the long-term complications.
One strategy of this invention is an attack on multiple pathophysiological processes by innovatively potentiating sulfonylurea. This is accomplished by combinations of biomolecules (some unique), biofactors and trace elements with disparate, although often complementary or synergistic, mechanisms of action in order to provide for better sulfonylurea management of the insulin resistance syndrome, more efficient prevention of type 2 diabetes, better management of type 2 diabetes and for prevention of long-term macrovascular and microvascular complications.
This invention enhances sulfonylureas"" insulin secretagogue effect and its effect on reducing glucose toxicity.
The complexity of type 2 diabetes pathophysiology provides the opportunity to expand sulfonylureas"" clinical usefulness by the administration of complementary, novel combinations of biomolecules, biofactors and trace elements, many of which are deficient or functionally inadequate in diabetics, or which may be unfavorably altered by sulfonylurea therapy.
The invention will enhance sulfonylureas"" efficiency by:
Reducing diabetic microvascular complications,
Modulating Ca2+ signaling and xcex2-cell membrane polarization,
Increasing insulin secretion and reducing hyperglycemia,
Maintaining synergy in the xcex2-cells between amino acids and sulfonylureas,
Inhibiting platelet aggregation,
Reducing norepinephrine (NE) release from cardiac sympathetic nerves.
The invention will expand sulfonylureas"" areas of effect by:
Reducing diabetic macrovascular complications,
Inhibiting mitochondrial-derived apoptosis,
Increasing the number of insulin receptors and the duration of action of insulin,
Increasing hepatic and peripheral insulin sensitivity,
Optimizing the xcex2-cell cytoplasmic free Ca2+ level,
Improving lipid profiles,
Reducing non-enzymatic glycation and advanced glycation end products,
Reducing the free radical effect at the caveolae and insulin receptor,
Reducing PAI-1 and improving fibrinolysis.
The invention will reduce sulfonylureas"" adverse effects by:
Reducing sulfonylurea-induced weight gain and inadequate fatty acid oxidation,
Reducing the sulfonylurea risk of hypoglycemia,
Reducing sulfonylurea gastrointestinal side effects,
Lessening the sulfonylurea hypofibrinolytic effect,
Reducing sulfonylurea-induced vasoconstriction.
This invention provides therapeutic amounts of a member of the sulfonylurea family of drugs combined with elements to enhance treatment of progressive insulin resistance and type 2 diabetes. This invention addresses sulfonylurea-induced mitochondrial malfunction and the failure of sulfonylurea to prevent diabetic macrovascular disease. It improves the useful antihyperglycemic effects of the sulfonylureas and adds an antihyperinsulinemia effect. It improves nocturnal control. It will in some patients provide at least a temporary substitute for insulin. The cumulative effect of this invention will extend the period of time that sulfonylureas can provide effective reduction of hyperglycemia.
By these various means, the invention will increase the number of patients who will benefit from sulfonylureas and the sulfonylurea-like oral antidiabetic drugs.
B. Biguanides (Metformin)
B.1. Metformin: Pharmacodynamics and Pharmacokinetics
The biguanides metformin (GLUCOPHAGEO(copyright)) and phenformin were introduced in 1957. Phenformin was withdrawn in many countries because of an association with lactic acidosis a complication with which metformin is only rarely involved. This invention focuses on the diethyl biguanide, metformin
Metformin has a unique mechanism of action and controls glycemia in both obese and normal-weight, type 2 diabetes patients without inducing hypoglycemia, insulin stimulation or hyperinsulinemia. It prevents the desensitization of human pancreatic islets usually induced by hyperglycemia and has no significant effect on the secretion of glucagon or somatostatin. As a result it lowers both fasting and postprandial glucose and HbA1c levels. It improves the lipid profile. It does not increase lactate production as much as other biguanides from skeletal muscle (e.g., phenformin): lactic acidosis associated with metformin use is rare (reported incidence of 0.03/1,000 patient-years exposure) and has occurred mostly in patients for whom the drug was inappropriate. Metformin can be safely used in the elderly, providing conservative doses are used.
Glucose levels are reduced during metformin therapy secondary to reduced hepatic glucose output from inhibition of gluconeogenesis and glycogenolysis. To a lesser degree it increases insulin action in peripheral tissues. Metformin also may decrease plasma glucose by reducing the absorption of glucose from the intestine, but this does not appear to be of clinical importance.
Metformin enhances the sensitivity of both hepatic and peripheral tissues (primarily muscle) to insulin as well as inhibiting hepatic gluconeogenesis and hepatic glycogenolysis. This decline in basal hepatic glucose production is correlated with a reduction in fasting plasma glucose levels. Its enhancement of muscle insulin sensitivity is both direct and indirect. Improved insulin sensitivity in muscle from metformin is derived from multiple events, including increased insulin receptor tyrosine kinase activity, augmented numbers and activity of GLUT4 transporters, and enhanced glycogen synthesis. However, the primary receptor through which metformin exerts its effects in muscle and in the liver is as yet unknown. In metformin-treated patients both fasting and postprandial insulin levels consistently decrease, reflecting a normal response of the pancreas to enhanced insulin sensitivity.
Metformin has a mean bioavailability of 50-60%. It is eliminated primarily by renal filtration and secretion and has a half-life of approximately 6 hours in patients with type 2 diabetes; its half-life is prolonged in patients with renal impairment. It has no effect in the absence of insulin. Metformin is as effective as the sulfonylureas in treating patients with type 2 diabetes, but has a more prominent postprandial effect than either the sulfonylureas or insulin. It is therefore most useful in managing patients with poorly controlled postprandial hyperglycemia and in obese or dyslipidemic patients; in contrast, the sulfonylureas or insulin are more effective in managing patients with poorly controlled fasting hyperglycemia.
B.2. Metformin: Effectiveness
Except perhaps for its appearance in aging, insulin resistance and type 2 diabetes do not usually occur in isolation, but as part of the complex metabolic-cardiovascular xe2x80x98Syndrome Xxe2x80x99, mentioned previously. Hyperinsulinemia and hyperglycemia are risk factors for all of the pathologies involved with the syndrome. Therefore, an initial recognition of these many intermingled relationships must precede the design of effective treatment of these entwined pathologies, and both hyperinsulinemia and hyperglycemia must be controlled if adverse macrovascular and microvascular complications are to be avoided. Long-term prospective studies have shown that treatment of hypertension and dyslipidemia reduces cardiac events in patients with type 2 diabetes. As an example, the United Kingdom Prospective Diabetes Study (UKPDS) showed that improved control of blood pressure reduced not only macrovascular complications (heart attacks, strokes, and death), but also the risk for microvascular end points by 37% (P=0.009). It is clearly important that pharmacological therapy not aggravate risk factors but leads to their improvement. Because obesity and physical inactivity are global risk factors for coronary artery disease as well as for diabetes, the need for weight loss and exercise must be stressed when diabetes initially is diagnosed, and must be reinforced throughout the natural history of the disease. However, modification of these may not be sufficient for clinical management. Metformin has been an attractive therapeutic aid.
Metformin is absorbed mainly from the small intestine. It is stable, does not bind to plasma proteins, and is excreted unchanged in the urine. It has a half-life of 1.3 to 4.5 hours. The maximum recommended daily dose of metformin is 3 g, taken in three doses with meals.
When used as monotherapy, metformin clinically decreases plasma triglyceride and low-density lipoprotein (LDL) cholesterol levels by 10% to 15%, reduces postprandial hyperlipidemia, decreases plasma free fatty acid levels, and free fatty acid oxidation. Metformin reduces triglyceride levels in non-diabetic patients with hypertriglyceridemia. HDL cholesterol levels either do not change or increase slightly after metformin therapy. By reducing hyperinsulinemia, metformin improves levels of plasminogen activator inhibitor (PAI-1) and thus improves fibrinolysis in insulin resistance patients with or without diabetes. Weight gain does not occur in patients with type 2 diabetes who receive metformin; in fact, most studies show modest weight loss (2 to 3 kg) during the first 6 months of treatment. In one 1-year randomized, double blind trial, 457 non-diabetic patients with android (abdominal) obesity, metformin caused significant weight loss.
Metformin reduces blood pressure, improves blood flow rheology and inhibits platelet aggregation. In part this results from the maintenance physiologic levels of constitutive NO; in part by attenuation of the agonist-stimulated (Ca2+) response in VSMC in parallel with the effect of calcium channel blockers.
Treatment of insulin resistance with metformin may also have important applications unique to women, particularly in polycystic ovary syndrome by reducing ovarian cytochrome P450c17 alpha activity and ameliorating hyperandrogenism. It is also possible that improving insulin sensitivity after menopause improves the cardiovascular prognosis of aging women.
These beneficial effects of metformin on various elements of the insulin resistance syndrome help define its usefulness in the treatment of insulin resistance and type 2 diabetes. These useful effects are enhanced when metformin is combined with components of this invention. The latter increase its effectiveness and efficiency, improve its safety and expand the arena of its medical benefit.
Unquestionably the UKPDS established that type 2 diabetes is a progressive disorder. Ideally, treatment with metformin (or a sulfonylurea, or insulin) would halt the progressive deterioration of glycemic control; this is not the case. For example: After an initial (and equivalent) decrease in elevated plasma glucose levels (HbA1c) of 1.5 to 2.0 percentage points, the long term rate of increase in this value during treatment with metformin (or a sulfonylurea, or insulin) was identical to that for a group treated merely with diet therapy. These results suggest that once overt fasting hyperglycemia has developed, the decline in glycemic control is relentless. In the UKPDS, this decline was related to deterioration of xcex2-cell function. The University Group Diabetes Program study similarly confirmed the progressive nature of type 2 diabetes. These important studies emphasize the need for constant reassessment of patients with insulin resistance and/or diabetes, and for appropriate adjustment of the therapeutic regimen in order to avoid hyperinsulinemia, deterioration or apoptosis of xcex2-cells and progressive loss of control over hyperglycemia.
Metformin reduces measurable levels of plasma triglycerides and LDL cholesterol and is the only oral, monotherapy, antidiabetic agent that has the potential to reduce macrovascular complications, although this favorable effect is attenuated by its tendency to increase homocysteine levels. Likewise, it is the only oral hypoglycemic drug wherein most patients treated lose weight or fail to gain weight.
This invention introduces a strategy to increase the safety and efficiency of metformin in suppressing recognized risk factors, thus slowing the progression of disease by extending both the duration and the breadth of metformin""s therapeutic value. The strategy of this invention will increase the number of patients by whom metformin can be used at reduced dose levels, thereby avoiding, delaying and lessening metformin""s adverse effects.
B.3. Metformin: Adverse Effects
Gastrointestinal side effects (diarrhea, nausea, abdominal pain, and metallic tastexe2x80x94in decreasing order) are the most common adverse events, occurring in 20% to 30% of patients. These side effects usually are mild and transient and can be minimized by slow titration. If side effects occur during titration, they can be eliminated by return to the dose at which no symptoms were encountered.
Metformin interferes with vitamin B12 absorption (an effect which is likely to be exaggerated in the elderly) and reduces serum vitamin B12 levels. This is a probable factor in the elevated levels of homocysteine (Hcy) which develop during treatment with metformin: the metabolism of Hcy depends on the vitamins B6, B12 and folate.
Lactic acidosis due to interference with the pyruvate oxidative pathway has rarely been reported with metformin use: a reported frequency of 3 cases per 100,000 patient-years occurs. However, patients with renal impairment should not receive metformin; since it is cleared by urinary excretion, severe lactic acidosis can result. Hepatic disease, a past history of lactic acidosis (of any cause), cardiac failure, and chronic hypoxic lung disease are additional contraindications to its use. These conditions all predispose to increased lactate production and hence to potentially lethal lactic acidosis.
This potentially fatal complication of biguanide therapy follows excessive circulating biguanide levels and is a greater risk in elderly patientsxe2x80x94especially those older than 80xe2x80x94in whom an age-related decrease in glomerular filtration rate is often seen. In such patients, it is recommended that creatinine clearance be measured before starting metformin therapy and that the metformin dose be minimized.
This invention, by specifically countering metformin side effects and/or by reducing the optimal metformin dose, will in turn, reduce the adverse effects of metformin therapy, while enhancing its beneficial effects. This is especially true for elderly patients. It may permit a least a limited number of patients with marginal renal and hepatic function to safely use metformin.
Metformin is included in formulations of this invention in order to better manage insulin resistance syndrome, avoid hyperinsulinemia and subsequent hyperglycemia, and help to provide ideal glycemic control. The concurrent delivery by this invention of active ingredients that complement metformin, comprise pharmacological approaches that will help to improve glycemic control by reducing the risks associated with specific abnormalities of several conditions and functions frequently associated with insulin resistance and/or type 2 diabetes. These include, among others, dysfunctional vascular endothelium, inappropriate apoptosis, undesirable platelet agglutination, inadequate maintenance of cell volume, dyslipedemia, hyperhomocysteinemia, xcex2-cell xe2x80x9cexhaustionxe2x80x9d or destruction, and the accumulation of advanced glycation end products.
B.4. Use of the Invention for the Prevention and Treatment of Insulin Resistance Syndrome and Type 2 Diabetes (Metformin+Other Active Ingredients).
As an individual progresses from often-covert insulin resistance toward and into type 2 diabetes, and has a corresponding need for drug therapy, metformin is often the drug of choice. However, because of limitations upon its chronic use and cumulative adverse effects, an increasing number of specific biomolecules, biofactors and trace elements, as shown in the following illustrations, become necessary to compensate for these deficiencies and adverse side effects. Other active ingredients of this invention are useful in correcting these adversities.
The present invention defines pharmaceutical formulations that contain metformin as one ingredient, for use as oral dosage forms which will increase the effectiveness, efficiency and safety of the treatment of insulin resistance and/or type 2 diabetes. In addition to metformin, the invention contains specific, sometimes unique, therapeutic biomolecules, biofactors and trace elements selected because of their particular and critical, combinational physiological effects in reducing adversities commonly associated with insulin resistance, type 2 diabetes and clinical biguanide use.
One strategy of this invention is to modulate multiple pathophysiological processes to innovatively improve the clinical use metformin. This is accomplished by combinations of active ingredients with disparate, although often complementary or synergistic, mechanisms of action in order to provide for better metformin management of the insulin resistance syndrome, more efficient prevention of type 2 diabetes, better management of type 2 diabetes and for prevention of long-term macrovascular and microvascular complications.
The invention will enhance metformin""s areas of influence in:
Reducing diabetic microvascular complications.
Modulating gluconeogenesis.
Reducing dyslipidemia.
Reducing hypertension (increase NO).
Reducing hypertension (modify dysfunctional calcium signaling).
Improving polycystic ovary syndrome.
Increasing insulin receptor sensitivity.
Inhibiting platelet adhesion and aggregation.
Reducing AGEs.
Reducing cell membrane damage from free radicals.
The invention will expand metformin""s areas of effect by:
Reducing diabetic macrovascular complications.
Inhibiting mitochondrial effected dysfunctional apoptosis.
Preventing progression from type 2 to xe2x80x9ctype 1.5xe2x80x9d diabetes.
Improving insulin secretion.
Modifying post-receptor disturbances of insulin resistance.
Increasing the number of insulin receptors and the duration of action of insulin.
The invention will prevent or reduce metformin""s dose-related adverse effects by:
Reducing gastrointestinal side effects.
Reducing hyperhomocysteinemia.
Reducing risk of lactic acidosis
This invention provides formulations that concurrently deliver metformin and other active ingredients for clinical use directed at enhancing the treatment of progressive insulin resistance and type 2 diabetes. By various means the invention will increase the number of patients who will benefit from metformin therapy.
C. Combined Biguanide (Metformin)-Sulfonylurea
The invention contemplates the concurrent delivery of therapeutic combinations of metformin and a member of the sulfonylurea family, in conjunction with other active ingredients. Situations may arise clinically in which a practitioner may wish to prescribe the concurrent use of metformin and a sulfonylurea, either in a single dosage form or as separate dosage forms, and concurrently prescribe a formulation which reduces known side effects of these drugs and which improves the efficiency of their use.
The above recitations describe benefits, side effects and deficiencies that arise from the individual use of metformin and of the sulfonylureas. Certainly all of the deficiencies and adverse effects that are listed may occur together in a single individualxe2x80x94it is more likely that the incidence of each adverse effect or deficiency should be considered a clinical variable with a significantly wide degree of incidence across patient populations. As a result, predicting the frequency and intensity of each adverse effect or deficiency for either metformin or for one of the sulfonylureas, becomes a statistical consideration of greater or lesser accuracy.
The clinical use of combinations of metformin and a sulfonylurea introduces more variables into this statistical calculation. Until sufficient clinical use of these combinations has occurred and has been evaluated, the existence or development of unique side effects and deficiencies cannot be known. It may rationally be assumed, however, that the side effects and deficiencies of each will statistically sort into about the same incidence currently present when each drug is used individually. However, whether or not some unknown adverse synergy may develop is not now predictable. It therefore cannot be therapeutically anticipated.
The invention contemplates that the formulations described individually as containing these two drugsxe2x80x94metformin or the sulfonylureas, along with the other active ingredients of this inventionxe2x80x94will be equally useful and effective when these therapeutic drugs are used concurrently.
The invention gives the practitioner an opportunity to provide concurrent complementary support for a widened spectrum of patients who are at risk of insulin resistance and type 2 diabetes, including those who require both metformin and sulfonylurea in combination.
Formulation Groups of this Invention (Active Ingredients Other Than Metformin or Sulfonylurea)
The active ingredients (other than metformin or a sulfonylurea) within the invention are organized into four functionally interrelated and interdependent, formulation groups: 1. Mitochondrial Metabolic Group, 2. Plasma and Mitochondrial Membrane Integrity Group, 3. Nocturnal Group and 4. Insulin Alternative Group. What follows is a summary. More extensive discussion of each ingredient is present further below in the document.
I. Mitochondrial Metabolic Group)
Metformin is involved in a cell-signaling pathway targeted to the mitochondrial respiratory chain complex I and has a persistent effect even after cessation of the signaling process. Mitochondrial abnormalities occur in the hepatocytes of patients with hyperhomocysteinemia via homocysteine-induced expression of the mitochondrial electron transport chain gene, cytochrome c oxidase III/ATPase 6,8. Homocysteine and H2O2 (but not H2O2 alone) causes a decrease in mitochondrial RNA levels, providing evidence that homocysteine and H2O2 act synergistically to cause mitochondrial damage. Homocysteine, associated with vasoconstriction, hypertension and thrombogenesis, tends to be elevated by metformin treatment. Metformin-induced hyperhomocysteinemia can be prevented by folic acid, a component of this group.
Sulfonylureas reduce available carnitine by restricting the renal reuptake of carnitine. In turn, this reduces the carnitine-directed transfer of long chain fatty acids into the mitochondriaxe2x80x94the main ATP (energy) source for the latter. Exogenous carnitine and choline (which lessens carnitine renal loss) tend to normalize the mitochondrial fuel supply. Taurine, often low in progressive insulin resistance and type 2 diabetes, is required to move Ca2+ into the mitochondria to signal ATP production. Magnesium is also necessary in the modulation of intracellular Ca2+: it works with mitochondrial-generated ATP to transfer excess cytoplasmic Ca2+ out of the cellxe2x80x94this transfer re-establishes cell membrane repolarization, which is necessary for sulfonylurea-metformin to activate the next shift of insulin into the bloodstream.
II. Plasma and Mitochondrial Membrane Integrity Group
The plasma membrane consists of a bilayer of amphipathic phospholipids that provides an anionically charged fluid barrier with selective permeability and selective active-transfer mechanisms. The membrane houses protein molecules in arrangements that support their functionality and provide a surface consistent with the needs of ligands. In the case of the vascular endothelium, this arrangement must provide a physiologic surface that is proper both for circulating cells and favorable luminal flow. If the cell membrane loses its integrity, Ca2+ modulation is impossible, endothelin-1(ET-1) increases and NO is induced into an iNOS Type II inflammatory condition: the latter contributes to inflammation and cell death, including pancreatic xcex2-cells. The sum of these events leads to further loss of membrane integrity. There now exists the proverbial circle in a spiral of, vascular degradation, local hypoxia, thrombogenesis and atrophy/apoptosis causing the macrovascular complications of progressive insulin resistance and type 2 diabetes.
The permeability transition pore, a multiprotein complex formed at the contact site between the mitochondrial inner and outer membranes, is the rate limiter of apoptosis. This mitochondrial permeability pore becomes dysfunctional (it opens) because of: (1) uncoupling of the respiratory chain within the membrane leading to the cessation of ATP synthesis, (2) hyperproduction of superoxide anions, (3) repletion or oxidation of non-oxidized glutathione, and (4) disruptions of Ca2+ homeostasis. These perturbations are lethal to the status levels of mitochondrial energy. Ubiquinone (coenzyme Q 10) is integral to the mitochondrial respiratory chain and additionally, working synergistically with xcex1-tocopherol, it reduces mitochondrial superoxide anions.
Some diabetic complications relating to cell membrane integrity may be worsened by sulfonylurea or metformin treatment.
Glutathione (GSH) is the most important intracellular defense against free radicals generated by mitochondrial metabolism and excess free radicals secondary to hyperglycemia. It becomes depleted in diabetes. Metformin increases available GSH in both diabetics and non-diabetics, indicating that it has some antioxidant activity that is independent of, and in addition to, its reductions of hyperglycemia.
GSH, a tripeptide, is not adequately absorbed from the gastrointestinal tract and requires a substrate; N-acetyl-cysteine is present in this invention as a GSH prodrug. GSH is conserved by the potent free radical scavenger xcex2-lipoic acid. Selenium is an imperative cofactor for glutathione peroxidase, which is required for optimized GSH activity. D-xcex1-tocopherol and ascorbic acid act synergistically to directly reduce peroxidation of membrane phospholipids, complimenting GSH. The combination of these ingredients stabilizes membrane proteoglycans, preserving the anionic charge necessary for normal permeability characteristics, which are imperative if diabetic micro and macrovascular complications are to be avoided.
L-arginine administration maintains the substrate necessary to permit normal, constitutive NO/cGMP. This balances the increased ET-1 of progressive insulin resistance, and compliments prostacyclin in maintaining the smooth, healthy, vascular endothelial surfaces required for normal, laminar blood flow.
Tetrahydrobiopterin (BH4) is an essential cofactor for nitric oxide synthase. In low concentrations of BH4, as is common in diabetes, nitric oxide synthase produces less constitutive NO and, correspondingly, larger quantities of the superoxide anion and hydrogen peroxide.
Excessive pancreatic xcex2-cell apoptosis is responsible for the irreversible progression toward insulin dependence found in type 2 diabetes. The integrity of the mitochondrial membrane is essential for preventing xcex2-cell dysfunctional apoptosis. The components of this group will inhibit the pre-mitochondrial (induction) phase of apoptosis caused by prooxidants, excessive cytosolic Ca2+ and elevations of induced NO.
III. Nocturnal Group
Sulfonylureas can increase the risk of nocturnal hypertension and decrease myocardial tolerance for ischemia and reperfusion. They do appear to have some antiarrhythmic effect in preventing ventricular arrhythmias induced by transient myocardial hypoxemia.
Nocturnal occurrences of myocardial ischemia/reperfusion events are common in progressive insulin resistance and type 2 diabetes, and the post-infarction mortality rate in these patients is double that of non-diabetics. Bedtime therapy, as defined in this invention, assists in reducing the nighttime risks of blunted nocturnal falls in blood pressure, myocardial ischemia and cardiac arrythmias; thereby complementing sulfonylurea and/or metformin treatment, and adding a dimension of protection against diabetic macrovascular complications.
The increased incidence of nocturnal myocardial ischemia and arrhythmias in progressive insulin resistance and type 2 diabetes relates to: (1) hypertension, (2) a blunted nocturnal fall in blood pressure, (3) hypoxemia induced by sleep apnea, (4) autonomic neuropathy, and (5) thrombogenesis. These are often interrelated. For example: in hypertension, sleep apnea syndrome and diabetes the normal nocturnal fall in blood pressure is absent or reversed. As another example: progressive insulin resistance causes hypertension and is associated with visceral obesity, which itself is a factor, along with insulin resistance, in causing sleep apnea. (See Reaven""s syndrome above.) As mentioned earlier, the sulfonylureas increase visceral obesity by interfering with normal fatty acid oxidation in the mitochondria.
The other active ingredients of this invention, used with sulfonylureas and/or metformin, will restore more normal circadian vascular physiology by: (1) reducing the nocturnal vasoconstriction related to hypertension and blunted nocturnal drops in blood pressure, (2) lessening cardiac autonomic neuropathy, (3) reducing thrombogenesis, (4) restoring physiologic fatty acid oxidation, and (5) reducing sleep apnea.
IV. Insulin Alternative Group
Oral antidiabetic monotherapy, while initially successful in reducing hyperglycemia, seldom succeeds for more than a few years. Even with combinations of antidiabetic oral agents many patients eventually require insulin. The introduction of insulin in patients being treated with sulfonylurea or with metformin increases the twin risks of hypoglycemia and weight gain. It also reintroduces the hyperinsulinemic risks that are associated both with progressive insulin resistance and with primary sulfonylurea or metformin treatment. The need for injectable insulin, however necessary, is a setback for the patient.
When hyperglycemia control inevitably fails in patients treated with metformin and/or a sulfonylurea, (upgrading to) this invention provides a temporary oral alternative to insulin. This is achieved by: (1) adding a natural insulin secretagogue, (2) supplying an insulin-mimetic substance, (3) increasing insulin receptor sensitivity, (4) increasing the number of insulin receptors, (5) improving insulin receptor binding, and (6) prolonging insulin action. These are discussed more extensively further below.
L-arginine is an insulin secretagogue that directly supports insulin binding to its receptor, and increases insulin receptor sensitivity via constitutive NO. Glucose uptake is augmented by increased perfusion of skeletal muscles secondary to L-arginine/NO-induced vasodilation: Insulin""s vasodilatation effect depends on insulin""s regulation of NO production by increasing the availability of cofactor BH4 needed for activation of NO synthase. Supplementation of BH4 is a logical insulin mimic in achieving vasodilation.
Vanadium mimics insulin intracellularly and prolongs insulin action. It increases both hepatic and peripheral insulin sensitivity, and activates glycogenesis, decreasing hyperglycemia. Vanadium preserves pancreatic xcex2-cells, and decreases diabetic hyperphagia, thereby improving both the safety and effectiveness of sulfonylurea and metformin.
Chromium, often deficient in diabetes, is a cofactor for insulin, increasing its binding to the insulin receptor and reducing insulin resistance. It increases the number of insulin receptors and facilitates insulin internalization by endocytosis from caveolae, thereby enhancing metformin""s beneficial effect on peripheral insulin sensitivity.
Zn2+ is involved with the synthesis, storage and secretion of insulin (thus aiding the sulfonylureas) as well as preserving its conformational integrity. At the insulin receptor site, Zn2+ prevents hyperglycemia by increasing insulin activity (aiding metformin); diabetics tend to have low plasma Zn2+ concentrations and decreased total body Zn2+, resulting in reduced insulin efficiency and hyperglycemia. Diabetics have increased urinary loss of Zn2+, which in turn contributes to hyperglycemia. This vicious cycle supports the use of supplemental Zn2+.
When added to an ongoing sulfonylurea and/or metformin regimen, this oral dosage form will usually be used in the evening, as is usually true when insulin is added. However, it is specifically designed to be used concomitantly and safely with daytime dosage forms of this invention, adding therapeutic complementarity without increasing risk. This provides the physician wide latitude of treatment options according patient need.
As an upgrade for combined sulfonylurea and/or metformin therapy, this invention will reduce sulfonylurea and/or metformin requirements and will prevent or delay the need for injectable insulin in type 2 diabetes.
Molecular Complexes Which May be Included in Formulations
The molecular complexes of this invention address various aspects of insulin resistance and type 2 diabetes such as 1) mitochondrial metabolism, 2) mitochondrial membrane integrity, 3) plasma membrane integrity, 4) adverse cytokine cascades, 5) dysfunctional xcex2-cell apoptosis, 6) inappropriate Ca2+ signaling, 7) insulin secretion, 8) insulin receptor sensitivity and 9) adverse effects of combinations of sulfonylurea-metformin.
1. xcex1-lipoic acid complexes
2. L-arginine or L-arginine ascorbate complexes
3. L-carnitine or L-carnitine ascorbate complexes
4. L-taurine or L-taurine ascorbate complexes
5. Tocotrienol nicotinate, tocotrienol picolinate
6. D,xcex1-tocopherol nicotinate, D,xcex1-tocopherol picolinate
7. Peroxovanadate-nicotinic acid (POV)
8. Propionylcarnitine taurine bi-amide
1. xcex1-Lipoic Acid Complexes
xcex1-Lipoic acid complexes included in the invention are used to increase the effectiveness, efficiency and safety of metformin and/or sulfonylureas in the prevention and treatment of progressive insulin resistance and diabetes mellitus. They have the following formulae:
[A]MX 
wherein
a. A is xcex1-lipoic acid or thioctic acid,
b. M is a metal ion taken from Mg2+ or Zn2+,
c. X is an anion taken from the group including hydroxides, halides, acetates or ascorbates acid salts.
or
M[A]
wherein,
a. A is xcex1-lipoic acid or thioctic acid,
b. M is a metal ion taken from Mg2+ or Zn2+.
The invention is a method for the oral administration of lipoic acid ascorbate or metallolipoate complexes, alone or in combination, as an active ingredient for humans. The cation of the metallolipoate complexes may be Mg2+ or Zn2+.
The compound is preferably administered in an oral daily dosage with Preferred and Most Preferred amounts of individual components as shown in the example below.